Brake Controller Tester

ABSTRACT

An apparatus is described that receives a brake control signal from the brake controller of a tow vehicle, and displays characteristics of that brake control signal including commanded brake force. The apparatus includes a data processor, brake simulation circuitry, brake integration circuitry, and display circuitry. The brake simulation circuitry sequentially applies several parallel resistors to the brake control signal in response to commands received from the data processor. These parallel resistors cause the load current on the brake controller to ramp up, mimicking the electrical signature of electric trailer brakes. At the same time, the brake integration circuitry integrates the brake control signal. Lastly, the display circuitry displays an indication of a value of the integrated brake control signal.

BACKGROUND OF THE INVENTION

Many newer vehicles that are likely to be used to tow trailers (i.e.,tow vehicles) come with integrated brake controllers designed to controlthe electric brakes on a trailer. Typically, the electric brake signalemanating from these integrated brake controllers is not a DC voltage,but is instead a train of pulses with widths that change with the amountof brake force desired. Stated another way, brake signaling is viapulse-width modulation (PWM). An advantage of PWM is that the electronicbrake controller circuitry is simplified and inherently more reliable.

As brake controllers have become more sophisticated, they have addedload monitoring circuits to identify a properly connected trailer. Newerbrake controllers are not only looking for a load but also the“signature” of a trailer's electric brakes.

Electric trailer brakes use an electromagnet to supply the brakingenergy to the trailer. Electrically, these brake magnets have the sameelectrical signature as a typical inductor. When a DC voltage is placedacross an inductor, the current rises from zero amps to its final valueover a period of time. Most of the newer electric brake controllers arelooking for this rising current function as an indication that theelectric brakes are properly connected and functioning. The controllersperiodically send a short power pulse to the brakes looking for thebrake magnet signature. If the signature is lost, the tow vehicle willwarn the operator that the trailer braking is either compromised ornon-existent. In some cases, the brake controller will stop functioningall together.

Both the pulsed brake signal and the load detection circuitry in modernbrake controllers make these devices more effective at accomplishingtheir tasks, but at the same time, more difficult for a technician totest for proper operation.

SUMMARY OF THE INVENTION

Embodiments of the present invention address the above-identified needsby providing brake testers that are capable of testing modern brakecontrollers by mimicking the electrical signatures of electric trailerbrakes.

Aspects of the invention are directed to an apparatus adapted to receivea brake control signal from a brake controller of a tow vehicle. Theapparatus comprises a data processor, brake simulation circuitry, brakeintegration circuitry, and display circuitry. The brake simulationcircuitry is adapted to sequentially apply a plurality of parallelresistors to the brake control signal in response to commands receivedfrom the data processor. The brake integration circuitry is adapted tointegrate the brake control signal. Lastly, the display circuitry isadapted to display an indication of a value of the integrated brakecontrol signal.

Additional aspects of the invention are directed to an apparatuscomprising a tow vehicle, a data processor, brake simulation circuitry,brake integration circuitry, and display circuitry. The tow vehiclecomprises a brake controller adapted to generate a brake control signal.The brake simulation circuitry is adapted to sequentially apply aplurality of parallel resistors to the brake control signal in responseto commands received from the data processor. The brake integrationcircuitry is adapted to integrate the brake control signal. Lastly, thedisplay circuitry is adapted to display an indication of a value of theintegrated brake control signal.

Even additional aspects of the invention are directed to a method ofdetermining one or more characteristics of a brake control signal from abrake controller of a tow vehicle. A plurality of parallel resistors aresequentially applied to the brake control signal in response to commandsreceived from a data processor. The brake control signal is alsointegrated. An indication of a value of the integrated brake controlsignal is displayed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 shows a front elevational view of a brake controller tester inaccordance with an illustrative embodiment of the invention;

FIG. 2 shows a block diagram of elements within the FIG. 1 brakecontroller tester;

FIG. 3 shows a schematic diagram of circuitry within the FIG. 1 brakecontroller tester; and

FIG. 4 shows a timing diagram of signals within the FIG. 1 brakecontroller tester.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described with reference to illustrativeembodiments. For this reason, numerous modifications can be made tothese embodiments and the results will still come within the scope ofthe invention. No limitations with respect to the specific embodimentsdescribed herein are intended or should be inferred.

As used herein, a “brake control signal” may comprise many differentforms. It may, for example, be in the form of a train of pulses likethose found when transmitting a signal via PWM.

FIG. 1 shows a front elevational view of a brake controller tester 100in accordance with an illustrative embodiment of the invention. Thebrake controller tester 100 includes a cable 110 and a plug 120, whichallow the brake controller tester 100 to be connected to atow-vehicle-side electrical connector of a tow vehicle. The brakecontroller tester 100 may thereby be placed in signal communication withthe brake controller of the tow vehicle. The cable 110 is attached to ahead 130 of the brake controller tester 100 via a connector 140.

In operation, the illustrative brake controller tester 100 is operativeto perform at least the following three functions:

-   -   1. Simulate a properly connected trailer to the tow-vehicle        brake controller;    -   2. Indicate the brake force being commanded by the tow-vehicle        brake controller; and    -   3. Indicate low brake force pulse amplitudes generated by the        tow-vehicle brake controller.        Commanded brake force is displayed via a cascading set of light        emitting diodes (LEDs) 150. Low brake force pulse amplitudes are        indicated by a “fault” LED 160.

FIG. 2 shows a block diagram of elements within the brake controllertester 100 that help to accomplish the above-described functions. Brakecontrol pulses, E_brake, from the tow-vehicle brake controller 200 arefirst sent to brake simulation circuitry 210, and then forwarded topulse integration circuitry 220. The combination of brake control pulsesE_brake combine to form the brake control signal. Two signals from thepulse integration circuitry 220, EBv and EBp, are then sent to amicrocontroller 230, which commands display circuitry 240 to displayboth the brake force being commanded by the tow-vehicle brake controller200, as well as any faults associated with low brake force pulseamplitudes. The display circuitry 240 includes the LEDs 150 and the LED160. The microcontroller 230 further sends three control signals,Q1_drv, Q2_drv, and Q3_drv, back to the brake simulation circuitry 210.The microcontroller 230 may be powered by a twelve-volt (12V) signalemanating from the tow vehicle and transmitted by the cable 110.

FIG. 3 shows a schematic diagram of the circuitry associated with thebrake simulation circuitry 210 and the pulse integration circuitry 220within the brake controller tester 100. As indicated in the BackgroundSection, many modern brake controllers include sophisticated circuitrythat periodically probe a trailer's brake system to determine if atrailer is in fact hooked up to the tow-vehicle and functioningproperly. Using the brake simulation circuitry 210, the brake controllertester 100 may simulate the signature of a magnetic brake system in anelectric brake (i.e., simulate the signature of an inductor) so as tofool the brake controller into believing that a trailer is connected tothe tow vehicle rather than the brake controller tester 100.

The brake simulation circuitry 210 emulates the signature of a brakemagnet with a set of resistors that are sequentially applied to eachbrake control pulse E_brake so that the load current felt by the brakecontroller during the pulse rises over time (i.e., the load currentramps up). As will be seen in the schematic in FIG. 3, the brakecontroller tester 100 in the present illustrative, non-limitingembodiment applies three resistors R1, R2, R3 in parallel to the linecarrying the incoming brake control pulses E_brake. Each resistor R1,R2, R3, in turn, is connected to a ground potential by a respectiveintervening transistor Q1, Q2, Q3, with each of these transistors Q1,Q2, Q3 controlled by a respective one of the control signals Q1_drv,Q2_drv, Q3_drv coming from the microcontroller 230. The microcontroller230 is thereby operative to independently turn on and off resistors R1,R2, R3, and is programmed to do just that when detecting brake controlpulses E_brake from the tow-vehicle brake controller 200.

The sequential application of resistors R1, R2, R3 to a particular brakecontrol pulse E_brake so as to emulate a magnetic brake is representedin a timing diagram shown in FIG. 4. Resistors R1, R2, R3 are turned onsequentially by the microcontroller when the brake control pulse E_brakeis detected by the brake controller tester 100. That is, upon detectingan E_Brake pulse from the tow-vehicle brake controller 200, themicrocontroller 230 sequentially turns on the three parallel resistorsR1, R2, R3 by sequentially driving control signals Q1_drv, Q2_drv,Q3_drv high so as to sequentially turn on the transistors Q1, Q2, Q3. Inone or more illustrative embodiments, resistors R1 and R2 may havesimilar resistances (e.g., 22 ohms), while resistor R3 may have asubstantially smaller resistance (e.g., 3 ohms). A ramping load currentis thereby created, simulating the presence of a brake magnet in anelectric brake. Once the brake control pulse E_brake has completed, themicrocontroller turns off resistors R1, R2, R3 by setting controlsignals Q1_drv, Q2_drv, Q3_drv low.

The brake controller tester 100 also displays brake force information tothe user. There are two signals of interest when determining brakeforce. The first is the average voltage during application of thebrakes. This is an indication of the brake force that a trailer willapply.

As indicated in the Background Section, modern brake controllers use PWMto supply the variable brake force to the trailer brakes. PWM is amethod of generating an analog voltage/current in the digital domain. Apulse train is generated, usually with a fixed frequency, where theratio of on time to total time is used to generate the desired voltage.The pulse train forms the brake control signal. Integrating the PWMsignal from the tow-vehicle brake controller 200 over time provides avalue indicative of brake force.

The pulse integration circuitry 220 integrates the brake control pulsesE_brake emanating from the tow-vehicle brake controller 200 over timewith a resistor/capacitor integrator. Referring again to FIG. 3,resistors R4, R5 and capacitor C1 form the integrator, and act togetherto output the average voltage in the form of the signal EBv. Themicrocontroller 230 receives the signal EBv and drives the multi-segmentLED display 150 in response to the magnitude thereof. The greater theapplied brake force, the greater is the magnitude of the signal EBv, andthe more LEDs 150 that are lit by the microcontroller 230 and thedisplay circuitry 240. Preferably, all the LEDs 150 are lit when thetow-vehicle brake controller 200 is commanding maximum brake force. Thedisplay circuitry 240 thereby displays an indication of the value of theintegrated brake control signal.

The brake controller tester 100 also measures the pulse amplitudes ofbrake control pulses E_brake and determines if those pulse amplitudesare near a specified battery voltage (e.g., 12V). If, for whateverreason, the pulse amplitudes are not close to the specified batteryvoltage, then even if the brake controller is trying to output 100%braking, the brake force signaled to the trailer may be less than 100%.Such a reduced amplitude could be caused by a weak battery or alternatorin the tow vehicle, defective components in the tow-vehicle brakecontroller 200, or a wiring issue between the tow-vehicle brakecontroller 200 and the brake controller tester 100. The signal EBp inFIGS. 2 and 3 provides a signal representative of brake pulse amplitudeto the microcontroller 230. Resistors R6, R7 act as a voltage divider.If the microcontroller determines that the signal EBp suggests that thebrake control pulses E_brake have low pulse amplitudes, themicrocontroller 230 commands the display circuitry 240 to cause thefault LED 160 to blink on the face of the brake controller tester 100.The rising and falling edges of the signal EPb also provide triggers tothe microcontroller 230 for the activation/deactivation of controlsignals Q1 dry, Q2 dry, Q3_drv.

While the brake controller tester 100 and the manner in which itfunctions are entirely novel, the circuit elements therein areconventional and may be readily acquired commercially. Transistors Q1,Q2 may comprise, for example, NDS355AN MOSFET transistors, whiletransistor Q3 may comprise a FQD13N10LTM MOSFET transistor. Both typesof transistors may be purchased from MOUSER ELECTRONICS® (Mansfield,Tex., USA).

The microcontroller 230 comprises one or more data processors (e.g.,central processing units (CPUs)) in signal communication with one ormore memories and one or more input/output peripherals. Many differentmicrocontrollers may be utilized. For example, in one or moreembodiments, the microcontroller 230 may comprise a PIC16F1513 8-bitmicrocontroller, also available from MOUSER ELECTRONICS®. Once thefunctions of the microcontroller 230 are understood from the teachingsherein, those functions may be programmed by one having ordinary skillin the programming arts. The programming of a microcontroller is,moreover, described in many readily available references, including, asjust one example, J. R. Smith, Programming the PIC Microcontroller withMBASIC, Newnes, 2005, which is hereby incorporated by reference herein.

The plug 120 on the brake controller tester 100 can take on severaldifferent forms so that it may interface with differently configured towvehicles. The plug 120 may, as just a few examples, be configured as a7-pin round blade connector, a 6-pin round connector, a flat 5-pinconnector, or a flat 4-pin connector. Nevertheless, this list is notintended to be exhaustive and should not be construed as limiting thescope of the invention.

Once the brake controller tester 100 is configured as set forth above,utilization of the apparatus to measure brake force is relativelysimple. The plug 120 is simply plugged into a tow-vehicle-sideelectrical connector of a tow vehicle, and the brake controller tester100 is monitored inside the vehicle while the brakes on the tow vehicleare modulated. Proportional brake controllers typically use an inertiasensor to detect the amount of brake force that a driver is commandingand automatically try to match that brake force at the trailer brakes.Therefore, it is contemplated that the brake controller tester 100 willbe utilized while the tow vehicle is being driven. The cord 110 istherefore preferably long enough to accommodate such a configuration.

The brake controller tester 110 has several advantages. As indicatedabove, many modern brake controllers must see the electrical signatureof an electric trailer brake, or will indicate a fault condition and notfunction. The brake controller tester 100, and more generally, apparatusin accordance with aspects of the invention, mimics the electricalsignature of such a brake without the use of actual magnets and, indoing so, provides a convenient, economical, and compact means by whichto test the brake force commanded by a modern brake controller.

It should again be emphasized that the above-described embodiments ofthe invention are intended to be illustrative only. Other embodimentscan use different types and arrangements of elements for implementingthe described functionality. For example, while the brake controllertester 100 utilizes one or more microcontrollers, other embodiments mayutilize discrete hardware instead. At the same time, alternativeembodiments may replace the cable 110 by a wireless connection (e.g.,Bluetooth connection). These numerous alternative embodiments within thescope of the appended claims will be apparent to one skilled in the art.

Moreover, all the features disclosed herein may be replaced byalternative features serving the same, equivalent, or similar purposes,unless expressly stated otherwise. Thus, unless expressly statedotherwise, each feature disclosed is one example only of a genericseries of equivalent or similar features.

Any element in a claim that does not explicitly state “means for”performing a specified function or “step for” performing a specifiedfunction is not to be interpreted as a “means for” or “step for” clauseas specified in AIA 35 U.S.C. §112(f). In particular, the use of “stepsof” in the claims herein is not intended to invoke the provisions of AIA35 U.S.C. §112(f).

What is claimed is:
 1. An apparatus adapted to receive a brake controlsignal from a brake controller of a tow vehicle, the apparatuscomprising: a data processor; brake simulation circuitry adapted tosequentially apply a plurality of parallel resistors to the brakecontrol signal in response to commands received from the data processor;brake integration circuitry adapted to integrate the brake controlsignal; and display circuitry adapted to display an indication of avalue of the integrated brake control signal.
 2. The apparatus of claim1, wherein the apparatus further comprises a connector adapted toconnect to the tow vehicle.
 3. The apparatus of claim 2, wherein theconnector comprises a 7-pin round blade connector, a 6-pin roundconnector, a flat 5-pin connector, or a flat 4-pin connector.
 4. Theapparatus of claim 1, wherein the data processor forms part of amicrocontroller.
 5. The apparatus of claim 1, wherein the data processoris powered by the tow vehicle.
 6. The apparatus of claim 1, wherein thebrake simulation circuitry further comprises a plurality of transistorscontrolled by the data processor, with each of the plurality oftransistors connected to a respective one of the plurality of parallelresistors.
 7. The apparatus of claim 6, wherein each of the plurality oftransistors is positioned between a respective one of the plurality ofparallel resistors and a ground potential for the apparatus.
 8. Theapparatus of claim 6, wherein the plurality of transistors aresequentially turned on by the data processor in response to the brakecontrol signal.
 9. The apparatus of claim 1, wherein the brake controlsignal comprises a train of pulses.
 10. The apparatus of claim 1,wherein the brake simulation circuitry causes a load current on thebrake controller to ramp up.
 11. The apparatus of claim 1, wherein thebrake integration circuitry integrates the brake control signal overtime.
 12. The apparatus of claim 1, wherein the brake integrationcircuitry comprises a resistor and a capacitor.
 13. The apparatus ofclaim 1, wherein the display circuitry comprises a plurality oflight-emitting diodes.
 14. An apparatus comprising: a tow vehiclecomprising a brake controller adapted to generate a brake controlsignal; a data processor; brake simulation circuitry adapted tosequentially apply a plurality of parallel resistors to the brakecontrol signal in response to commands received from the data processor;brake integration circuitry adapted to integrate the brake controlsignal; and display circuitry adapted to display an indication of avalue of the integrated brake control signal.
 15. The apparatus of claim14, wherein the brake simulation circuitry causes a load current on thebrake controller to ramp up.
 16. A method of determining one or morecharacteristics of a brake control signal from a brake controller of atow vehicle, the method comprising the steps of: sequentially applying aplurality of parallel resistors to the brake control signal in responseto commands received from a data processor; integrating the brakecontrol signal; and displaying an indication of a value of theintegrated brake control signal.
 17. The method of claim 16, wherein thestep of sequentially applying the plurality of parallel resistors to thebrake control signal causes a load current on the brake controller toramp up.